This invention relates to methods and apparatus suitable to remove particles from effluent waste, and particularly, to remove amalgam and other metallic particles and other abrasive solids from dental office suction effluent.
Although amalgams are less frequently used for new dental fillings than was the case some decades ago, nevertheless, amalgams continue to comprise a significant portion of the metallic particle component of dental office effluent because of the fact that old fillings comprising amalgams are drilled out and removed in the effluent waste when new fillings are effected to replace the old. Further, even under current dental practice, an amalgam is preferred for some tooth filling situations. The use of an amalgam in a filling is never a 100% efficient process; amalgam residues are discharged into the dental office effluent. Typically, dental amalgam comprises a number of metals, invariably of course including mercury and almost always at least some silver. Because mercury is a poison that can accumulate in living tissues and can pose a health hazard to species in a food chain exposed to mercury-containing compounds, and since humans are inevitably at the end of the food chain, it follows that effluent containing amalgams can pose a health hazard to the community at large. Also, certain metals such as silver are commercially valuable if recovered in quantity. For those reasons, it is desirable to devise apparatus and processes for removing amalgams from dental office effluent. In addition to removing amalgams, other matter disposed into dental office suction effluent includes aluminum oxides used in air abrasion treatments and other solid waste material. These solid materials tend to wear out or damage vacuum pumps and other equipment downstream of the dental chair suction apparatus, and also constitute effluent water contaminants. Therefore, it is desirable for the apparatus to remove solid abrasive material and other particulate waste from the dental office suction effluent.
Previously known apparatus for removing amalgam particles from dental office suction effluent are known to include a collecting tank for collecting a working day""s accumulation of suction effluent from one or more sources of such waste. The waste is sucked from the dental chair suction apparatus and into the collecting tank by a vacuum pump. When the vacuum pump is turned off, an outlet valve is opened and the accumulated waste is deposited into a separation device intended to separate metal particles from the effluent liquid. Flow into the separation device is induced by the head of fluid in the collecting tank. Particles passing through the separation device are separated from the waste by gravity and settle to the bottom of the separation device. The flow rate is dependent on the head inside the collecting tank; as the head diminishes, the flow rate also diminishes. The changes in flow rate are undesirable because the particle separation rate is affected, and the system becomes prone to plugging when the flow rate decreases. Also, since the waste can be deposited only when the vacuum pump is off, waste is usually moved to the separation device at the end of the day. As a result, the collecting tank and separation device tend to be undesirably large.
Another known apparatus is a centrifuge type system that separates heavier metal particles from effluent liquid by collecting the particles at the peripheral wall of the centrifuge. This apparatus does not effectively separate lighter particles, and is expensive to purchase and operate due to the complexity of its mechanical parts.
Yet another known apparatus uses a dedicated mechanical pump to suction waste liquids through a separator device. Again, a dedicated pump can be expensive to purchase and to maintain, and can be undesirably space-consuming.
Such known systems can become quite complex, unwieldy and expensive, as for example that disclosed in Ralls U.S. Pat. No. 5,885,076 granted Mar. 23, 1999. Ralls teaches the use of sedimentation, co-precipitation and filtration in an expensive complicated apparatus that is probably economical, if at all, only for relatively large installations such as a military base dental complex.
An alternative approach described in Ludvigsson U.S. Pat. No. 5,205,743 granted Apr. 27, 1993 involves provision of an air flow in the vicinity of the patient""s mouth and suction from that air flow; such apparatus is designed to remove mercury vapour present in the air flow.
The present invention overcomes some of the shortcomings of the prior technology and achieves further advantages that will be apparent after reviewing the following summary of the invention and detailed description.
According to the invention, an apparatus is provided for removing metal-containing particles and other waste particles from effluent, particularly effluent from a dental office. While herein the term xe2x80x9cmetal particlesxe2x80x9d will frequently be employed, it is contemplated that the apparatus is fully capable of separating other solid particles from effluent liquid. Further, with the aid of one or more precipitants, selected solutes may also be removed. In a particular application to be described in detail, effluent from a dental office suction apparatus is discussed; the metal particles are primarily amalgam particles made of mercury and silver alloyed together in an amalgam composition, sometimes with other metals. The metal particles may be in solid particulate form suspended in the liquid, or may be in solute form dissolved in the liquid. The solid particles other than amalgam residues include aluminum oxides used in air abrasion treatment, enamel and dentin from teeth, porcelain, acrylic used in bridges, and prosthetic cementing agents such as zinc phosphate cement used in crowns and bridges. These solid particles are typically suspended in the liquid effluent. Herein such particles are sometimes collectively referred to as xe2x80x9ctarget particlesxe2x80x9d, since they are targeted for removal from the effluent. Such target particles also include precipitated particles obtained in the effluent suspension by precipitation of solutes out of solution.
According to one aspect of the invention, an apparatus for removing metal particles and other solid particles from liquid suction effluent can be installed in a dental office using a pre-existing suction/vacuum pump system to provide fluid flow through the apparatus, without requiring dedicated fluid-flow provenance devices. The apparatus may share a common vacuum pump with conventional dental chair suction apparatus, without interrupting the use of suction equipment at the dental chairs.
Removal of solid particles from liquid suction effluent may be effected by a combination of sedimentation and filtration, assisted by flocculation and precipitation. The invention is not concerned with the specific choice of sedimentary deposit apparatus, a preferred implementation being presented herein as a suitable exemplification of such apparatus. Nor is the invention concerned with specific choices of precipitants, coagulants, flocculants, or other associated materials to effect or facilitate removal of solids or solutes; rather, the invention is concerned with the overall system of solids removal, the provision of apparatus and methods for controlling flow of liquids and gases therein, and the facilitation of removal and replacement of deposit tanks that have been filled with solid waste.
In accordance with a preferred embodiment of the invention, the dental office suction effluent is passed from dental chair suction equipment outlets to a surge tank via a suitable inlet port for the surge tank. The surge tank in turn passes effluent into a sedimentary deposit tank, closed on all sides when in use and preferably readily detachable for emptying and replacement. The sedimentary deposit tank in a preferred embodiment has a series of interior walls that separate the interior of the sedimentary deposit tank into a consecutive series of baffle chambers, including an inlet baffle chamber at the beginning of the series and an outlet baffle chamber at the end of the series. The inlet baffle chamber receives effluent through an inlet port, situated in the preferred embodiment in the lid of the sedimentary deposit tank. The baffle chambers in between the inlet and outlet baffle chambers each in turn receive effluent passed to such chamber by the preceding such baffle chamber in the series. So, liquid effluent flows from the inlet baffle chamber through the interconnected series of baffle chambers to the outlet baffle chamber from whence it passes via a deposit tank outlet port, and preferably thence to an auxiliary filtration unit, as will be further described below.
In such preferred sedimentary deposit tank, each baffle chamber, or at least some of them, receive removable baffles composed of inverse V-shaped strips, inclined either in one dimension, resembling a chevron, or in two dimensions, resembling a gable in appearance. Such baffles are arranged and joined to form channels bounded above and below by the baffle or sedimentary tank surfaces and the side walls of which are formed by the interior divider walls of the baffle chamber into which each baffle is individually inserted. Further, the transverse width of each baffle must be less than the transverse width of the sedimentary deposit tank such that after the insertion and centering of the baffle inside the corresponding baffle chamber, there are apertures between the side walls of the sedimentary tank and the edges of the baffles to allow for the effluent to access and exit the channels formed by the baffles and baffle chamber walls.
In a preferred embodiment of the invention designed to minimize manufacturing costs, the baffles in the baffle chambers are individually formed, configured and dimensioned so that they can be vertically stacked on top of each other or aligned end to end within the baffle compartment. In another preferred embodiment of the invention designed to minimize the costs of assembling sedimentary tank equipment, several vertically spaced baffles are integrally formed as a unit, the configuration and dimensions of such integral baffle units and the baffle compartments selected so that just one integral baffle unit fits into each compartment. Such chevron or gable-shaped baffles or multi-surface integral baffle units can be cheaply and easily manufactured in quantity and simply inserted into a mating baffle compartment without requiring any fasteners, and removed just as easily for cleaning or replacement. In a further embodiment of the invention that provides for additional effluent flow paths through an individual baffle chamber thus promoting efficient sedimentation, two sets of inclined baffle surfaces, each of approximately half the width of an individual baffle chamber, may be fixedly attached on opposite sides of a vertical dividing wall to provide a single unit that can be removably inserted into a compartment of the sedimentary deposit tank. Alternatively, in the interest of modular design, baffle surfaces may be fixedly attached to the baffle chamber walls, such walls being designed to be easily removable from the sedimentary deposit tank for cleaning or replacement of the fixedly attached baffle surfaces.
Each transverse baffle chamber wall of the preferred sedimentary deposit tank separating each baffle chamber from its neighbouring chamber or chambers, extends from the floor of the chamber to a top edge of the chamber and has a notch on its top edge. The bottom edge of each notch is positioned on a pass-over height that is common to all of the chambers. As described above, the water successively enters, passes through the baffle channel and exits each baffle chamber; accordingly, for the baffle chamber to be functional, the horizontal position of the openings (comprising notches and inlet and outlet ports) in each two neighboring chambers must alter in transverse position, so the fluid can enter each chamber on one side, pass through the channel formed by the baffle and exit the chamber on the other end. Because all the notches in one sedimentary deposit tank are preferably at the same vertical level, the second baffle chamber (the neighbour to the inlet baffle chamber immediately downstream thereof) can receive liquid only when the inlet baffle chamber is full and liquid passes over the notch on the intervening transverse baffle chamber wall once it has reached the pass-over height. Similarly, liquid can pass from the second baffle chamber to the third only after the second baffle chamber is full and liquid passes over the notch on top of the wall of the second chamber at the pass-over height to enter the third baffle chamber, and so forth up to the final outlet baffle chamber. When the outlet chamber becomes full, it passes liquid out of the sedimentary deposit tank via the outlet port. In a preferred embodiment of the present invention, the baffle chamber walls are integrally formed as a fixed part of the sedimentary tank structure. Alternatively, however, the baffle chamber walls may be separately formed and removably configured to engage slots in the walls and floor of the sedimentary deposit tank, the slots holding such baffle chamber walls in place inside the sedimentary deposit tank. Optionally, inclined baffle surfaces may be fixedly attached to such removable baffle chamber walls, as mentioned above.
In each baffle chamber, the target particles, being on the average heavier than the liquid effluent, will tend to sink to the bottom of the baffle chamber. Those target particles that are not collected in the first baffle chamber have a chance to be collected in the second, and so on in sequence to the final outlet baffle chamber, so that overall there is a good chance that at least the heavier target particles will be collected at the bottom of the various baffle chambers. Further particle separation can be effected by passing the suction effluent through a plurality of screens or filters positioned in some of the baffle chambers. In a preferred embodiment of the invention, such screens or filters may be located in the final (downstream) baffle chamber or final few baffle chambers to remove particles remaining in the effluent after sedimentation in upstream baffle chambers has taken place before effluent exits the sedimentary deposit tank. Removal of dissolved solute metal particles from the effluent liquid can be achieved by adding a suitable chemical agent such as a precipitant, chelating agent or coagulant, or some combination thereof to the effluent being processed in the sedimentary deposit tank, such chemical agent(s) being selected for combination with solute mercury or silver or both, it being an important objective to remove solute mercury particles, and an objective also to remove solute silver particles from the effluent. The chemical agent precipitates out of the solution metal particles that are in solute form and may facilitate formation of larger particles from smaller particles. Among suitable such agents are precipitants such as potassium iodide (KI), potassium iodate (KIO3), sodium sulfide (Na2S) and various other sulfur compounds; a preferred chelating agent is sodium ethylenediaminetetraacetic acid (sodium EDTA).
The chemical agent(s) may conveniently be injected into the effluent being processed in the sedimentary deposit tank by means of one or more inlet ports preferably located at or near the top of the second or third baffle chamber so that after the largest particles have settled out of solution in the first or second baffle chambers, the chemical agent(s) may act on the entirety of the liquid passing through the remaining downstream baffle chambers in sequence.
If desired, a time-dependent delivery apparatus may provide a metered amount of chemical agent via one or more inlet ports to the second or third baffle chamber, or the chemical agent(s) may be added on a flow-rate-dependent basis, as preferred. The amount of agent added per unit of time or per unit of effluent flow will be dependent in part upon the chemical characteristics of the agent(s) employed, and in part upon the expected concentration of particles in the effluent liquid, and is usually best determined empirically. Accordingly, the amount of chemical agent added to the settlement tank baffle chamber per unit of time or per unit of effluent passing through the baffle chamber is preferably adjustable. According to one aspect of the invention, the introduction of such chemical agent(s) is automatically regulated to occur only when the dental office suction apparatus is operating actively; an overnight shutdown will occur without intervention.
As an alternative to or in combination with the addition of chemical agents such as precipitants, flocculants and chelating agents to the effluent, an adsorbent compound may be used to remove metal ions from solution by surficial adsorption. Such a compound may be incorporated in the construction of the interior of the system settlement tank whereby metal ions dissolved in the effluent passing through the tank are adsorbed by the adsorbent material. A preferred adsorbent material is bentonitic clay. In a preferred embodiment of the present invention, finely divided bentonite clay particles are combined with activated silica particles and enclosed in a porous and permeable membrane, similar in function and appearance to a tea bag. Such bentonite and silica filled membrane may preferably be located in the final few baffle chambers of the sedimentary deposit tank whereby dissolved mercury and other metal ions may be adsorbed by the bentonite, and organic compounds may be adsorbed by the silica prior to the effluent exiting the tank through the tank exit port.
In order to control the growth of bacteria, yeasts, molds, fungi and viruses in the effluent treatment system, a disinfectant is added to the effluent at the individual operatory suction openings. In the preferred embodiment of the invention, the disinfectant is chlorine, bromine or peroxide based, and utilized in a solid dissolvable form.
The flow rate at which the effluent passes through the individual baffle chambers in the sedimentary deposit tank is an important feature of the solid removal system. Precisely, it is desirable to have as slow a flow rate of effluent as possible, to maximize the time for the particles to separate from the effluent in the sedimentary deposit tank. The flow rate of effluent through the sedimentary deposit tank is preferably maintained at a relatively constant value and may be regulated to this end. However, the flow rate may be changed if, for example, the surge tank becomes backed up with effluent. A typical dental office disposes of about one liter of suction effluent per chair per working day, but this quantity may be higher if a cuspidor drain is also connected to the suction apparatus (which may be desirable in the interest of preventing additional undesirable mercury-containing particles from entering the ecosystem, although it is undesirable in that it will typically require a larger-sized separation apparatus to handle the larger volume of effluent). The optimal flow rate setting can be estimated empirically as being equal to the total volume of effluent generated during a duty cycle (for example an 8 hour working day), divided by the total available time for operating the sedimentation system per duty cycle, the resulting rate multiplied by an appropriate safety factor (greater than 1.0) to guard against backup of the system to give the optimal flow rate. For this purpose, not only are the elements of the apparatus according to the invention suitably selected for dimensions, capacity, vacuum level, etc. (this may be done empirically), but also a flow meter and needle valve or other suitable flow regulator may be installed to control the rate of outflow from the sedimentary deposit tank. The needle valve is adjustable to change the flow rate by changing the valve orifice size. The flow meter measures the flow rate of effluent exiting the sedimentary deposit tank and displays the flow rate measured, permitting the operator to adjust the flow by adjustment of the needle valve. While alternative automatic or semi-automatic feedback control of the flow can be devised, it would be expected to add appreciably to the cost of manufacture of the equipment.
Although the sedimentary deposit process is effective to remove a satisfactorily high proportion of the target particles desired to be removed from the effluent, the sedimentary deposit tank desirably includes an outlet screen filter in the final baffle chamber to catch any floating materials as well as any other materials that did not settle out in the upstream baffle chambers. Downstream of the sedimentary deposit tank, an auxiliary filtration unit to filter out finer solids may be provided, and a mercury vapour filter may be provided in the air bypass conduit. In the preferred embodiment of the invention, the auxiliary filtration unit is incorporated into the construction of the sedimentary deposit tank and may be located in the final baffle chamber of the tank.
Desirably, at least the sedimentary deposit tank and optionally various filtration units may be connected to the system as removable modular units, or if the filtration unit is desired to be removed independently of the sedimentary deposit tank, each of the sedimentary deposit tank and filtration unit may be devised as removable modular units. For heavier volume effluent processing, two or more sedimentary deposit tanks may be coupled into the system in parallel or in series. It is expected that modular design will be most efficacious for dental offices because it is not to be expected that dentists or their staff will be effectively able to remove deposited sediment from the sedimentary deposit tank nor remove accumulated particle residues from the filtration unit. It is desirable that such removal be done by a competent effluent residue processing facility. Therefore, it is expected to be preferred that the modular sedimentary deposit tank and/or filtration unit be removed periodically and replaced by fresh such tanks or units from time to time as required. The spent tank or unit with an accumulation of metallic particles can then be sent to a processing facility for removal of the metallic particles, possibly chemical separation of mercury from silver, etc., and cleaning of the modular units for re-use. However, if, in any particular installation, it is desired instead that onsite removal of particles be effected, then suitable bypass valves should be provided at the appropriate fluid flow ports, and means provided for removal of particles (e.g. for the sedimentary deposit tank, the entire top wall might be opened or removed, and for the filtration chamber, an access door provided to permit replacement of filters and removal of particles, etc., according to the designer""s preference).
Further, according to another aspect of the invention, a full sedimentation tank may be disconnected from active use, and connected to a suction attachment to transfer excess waste water from the sedimentation tank into the surge tank which waste water in turn is retreated in the replacement sedimentation tank. The full tank may then be coupled into a drying conduit connection for a period of time and exposed to tank-drying airflow to permit liquid in the tank to vaporize and be removed in the air outflow. A dry tank is easier to handle by waste processing service personnel than a tank containing a large volume of liquid. Further yet, monitoring means may be provided to determine when the solids content of a sedimentary deposit tank has reached a predetermined level, so as to facilitate transfer of the effluent to a previously idle sedimentary deposit tank.
For the apparatus to work to best advantage without dependence on gravity, a pressure differential must be maintained between the inlet port of the surge tank and the outlet port of either the filtration unit or the outlet port of the sedimentary deposit tank if no filtration unit is present. To this end, the air pressure at the system outlet is maintained at a level less than the air pressure at the system inlet. Assuming that the system operates by using a vacuum pump, the pressures in question are below atmospheric pressure. The system requires that air enter the inlet either via the dental chair suction devices or via a separate air inlet, preferably a vacuum break valve as described below. Consequently, in a vacuum system, the inlet pressure is nearer (but below) atmospheric pressure, while the downstream pressure at the separator outlet is nearer the pressure drawn by the vacuum pump. This pressure differential causes an overall flow of effluent fluid through the surge tank, into the sedimentary deposit tank, thence to the auxiliary filtration unit (if present), to exhaust via the separation system outlet into the vacuum pump exhaust line.
A vacuum pump may apply a partial vacuum at the system inlet port, while at the system outlet port, the vacuum pump draws a higher vacuum, so that there is a pressure differential sufficient to drive effluent liquid properly through the separator system. A pressure differential of the order of 3-10 kPa between inlet and outlet vacuum levels is sufficient to cause liquid effluent to flow through a small simple system, but depending upon the pressure drops within the system, the size of ports, passages, chambers, viscosity of the effluent, etc., the pressure differential may have to be higher. It is best, again, to take an empirical approach and permit the pressure differential to be adjusted manually to suit the user""s requirements.
In order to maintain constant air flow through the apparatus when the vacuum pump is operating, there is a spring-loaded vacuum break valve that opens when the suction apparatus openings from the dental chairs are all closed. (Depending upon the spring force exerted on the vacuum break valve, the valve will remain closed when the suction equipment of one or more dental chairs operates, and the requisite input air to the system will be provided via the dental chair suction apparatus.) When the vacuum break valve is opened, the top of the surge tank is open to the ambient air, and suction through the apparatus is effected, causing fluid to flow through the apparatus.
The required air pressure differential between inlet and outlet can instead be positively applied by an air pressure source, but in that event, some means must be interposed at the surge tank to prevent air pressure from driving effluent upstream. According to an aspect of the invention, an additional regulator valve for the surge tank may be provided to accommodate a positive air pressure. The positive air pressure is applied during intervals between successive active operation of the suction drainage system from dental chairs. As dental offices invariably have a source of air under pressure, this source may be used to provide a positive air pressure differential.
If the surge tank becomes full, overflow effluent is sucked through the air outlet port and discharged into the air bypass conduit, thence to the vacuum pump draw line and thence eventually into the municipal drain. However, it is desirable that the system should operate in such a manner as to avoid having the surge tank become completely full, since effluent exiting through the air outlet port will contain particles that will not be separated by the separator. Even if a pinnacle filter or the like catches some of these particles, solutes and some finer solid particles would be expected eventually to be discharged into the municipal drain. A user of the separator accordingly may wish to adjust the pressure differential of the vacuum system or the size of a constriction in the outlet conduit for the separator, or otherwise suitably adjust the flow rate through the system to prevent overflow. The users may also temporarily suspend discharge of large quantities of liquid into the dental chair suction apparatus if the surge tank is on the verge of becoming full.
It is accordingly preferable that one or more liquid level sensors for sensing liquid level within the surge tank are provided that will cause suitable warning signals to be displayed or heard as the liquid level in the surge tank increases. For example, the sensing mechanism could sense when the surge tank is xc2xc full, xc2xd full, xc2xe full, and xe2x85x9e full, and at each threshold liquid level within the surge tank, could provide a suitable warning signal (perhaps using lamps of different colours to correspond to different threshold levels, etc.). Further, when the liquid level in the surge tank has reached (say) the xe2x85x9e level, it may be desirable to alert the users of the system by a more urgent signal (e.g. an audible signal) so that the users will be more urgently warned of the risk that the surge tank may soon be full.
It is also desirable to monitor solids levels in the sedimentary deposit tank or tanks. Solids should preferably accumulate in such tanks only to a fraction of the total tank volume so as not to interfere unacceptably with the settlement process within baffle chambers. As baffle chambers fill up with solids, liquid flow through the tank becomes impeded or deflected and the tank becomes increasingly less effective to promote settling out of solids. In this specification, reference to a xe2x80x9cfullxe2x80x9d sedimentary deposit tank that should be removed and replaced by a fresh tank, or cleaned out, implies a tank filled with solids to the extent that the user of the system or its designer considers to be acceptable, but does not imply a tank totally filled with solid waste.
Monitoring of solids level within the sedimentary deposit tank may be conveniently be accomplished by a sensor responsive to variations in dielectric constant installed at an appropriate location on an exterior wall of the settlement tankxe2x80x94atop the lid or at the bottom of the sedimentary deposit tank, or preferably at a threshold level position along a side wall. Similar such dielectric-constant variable capacitance-type sensors are commonly used as stud finders for locating studs in closed walls. The location of the sensor on an exterior side wall of the settling tank, so that the sensor path is generally horizontal, may be more reliable in that the distinction between liquid and solids in the path of the sensor is more pronounced than the gradual change in dielectric constant that would be sensed by a sensor atop the tank lid whose sensor path is vertical. In either case, the operating principle is the same while the solids level in the tank is below the threshold level established for warning detection by the dielectric sensor, no warning signal is supplied, but when the solids level rises to the threshold level above which the sensor provides a warning signal in response to the change in dielectric constant of the solids in the detection path of the sensor, a suitable alert signal (audible, visual, or both as required) can then warn the user that the tank is adequately full and should be removed and replaced, or cleaned.
Monitoring of flow activity within the sedimentary deposit tank may be conveniently be accomplished by a sensor responsive to changes in dielectric constant between effluent liquid and air installed at the top of the tank. When the dental office is working actively, the sedimentary deposit tank quickly fills up and liquid rises to at least some extent in the surge tank. When the office shuts down for the day, effluent drains out of the top of the tank to the extent permitted by the outflow conduit, leaving at least some empty space at the top of the tank. If the dielectric liquid level sensor is installed in that space, the sensor will be responsive to the change in dielectric constant detected when the liquid level in the tank falls below the sensor location. A chemical agent supply pump can be controlled by a suitable control circuit which is responsive to the dielectric liquid level sensor accordingly supply precipitant or other chemical agents at a constant rate determined by the pump to the tank when it is operating, but to shut off when the liquid level in the tank falls below the sensor location. This of course may happen during slack times as well as overnight and on weekends, etc.
The particular sensing devices chosen for sensing liquid level within the surge tank, the warning signal devices and the electrical means for actuating them can all be of conventional design and are not individually per se part of the present invention.
While the invention using a vacuum system is operable if its vacuum source or other source of pressure differential is not connected to the vacuum source for the dental chair suction apparatus, it is convenient and considerably less costly to use a single vacuum pump to serve both the dental chair suction apparatus and the separator apparatus. While, as mentioned, positive air pressure may be used instead of an air pressure differential maintained by vacuum, the system may be somewhat less complex and less expensive to manufacture if a vacuum system is used throughout, utilizing the vacuum pump already present in the dental office.
In a further embodiment of the invention oriented towards large-scale institutional applications in which many dental chairs or other sources of effluent are connected to the same suction and drain services, several parallel-connected sedimentary deposit tanks and associated apparatus, each such composite apparatus including a surge tank and preferably one, or alternatively two attached sedimentary deposit tanks, may be operated in parallel to provide sufficient treatment capacity for large effluent volumes. In such large installations, fluid flow through the individual sedimentary deposit tanks may be controlled by the flow gauge and needle valve means disclosed above, or may preferably be controlled by one or more separate auxiliary effluent vacuum pumps in order to reduce the complexity of adjusting multiple needle valves (or similar individually adjustable flow control devices for each tank) to equalize effluent flow through multiple deposit tanks.
While the invention has been described in the context of a dental office and is expected that dentists will be the primary users of the invention, the invention has application to other similar effluent separation situations. For example, with suitable changes to meet particular situations, the invention may be adapted for use with jewellers"" effluent, diamond cutting effluent, dental laboratories effluent, and the like. Where the effluent contains potentially valuable recoverable solids, filters and other removal apparatus and procedures should be selected to maximize the recovery. Equally, for pollution control, recovery of environmental contaminants may be desirable.